Philip II reigned in Macedonia between 359 and 336 BC. Tetradrachms like this one are prevalent during this period. The head is of Zeus, with the back showing a youth on horseback.
Tetradrachms are made of silver and weigh about 14 to 15 grams (about 25 mm diameter). There are also bronze coins of the period with similar patterns, but they weight substantially less and are worth about one-quarter of the tetradrachm price.
As with all ancient coins, prices vary considerably and each coin stands on its own merits. The coin in our photo comes from Numismatica Ars Classica and sold for 1300 Swiss francs (about the same number of US dollars) during a 2015 auction. Classica's coin is in superb condition with tremendous eye appeal, and this sends value way up. Very approximately:
worn: $100 US dollars approximate catalog value
average circulated: $500
well preserved: $1800